There is a mentality that this hurts property values and higher density means bringing poverty and undesireables in. Nothing to do with psyche.
A detailed analysis  concluded that the RHIC collisions were comparable to ones which naturally occur as cosmic rays traverse the solar system, so we would already have seen such a disaster if it were possible. RHIC has been operating since 2000 without incident.
Phew! I was worried that I overslept and missed the Strangelet singularity! Talk about stating the obvious.
Wikipedia: -1 Redundant
To do two things at once is to do neither. -- Publilius Syrus